cunningham



Jne 25, 1934- v L. L. CUNNINGHAM ACOMPENSA'IEI) PILOT DEVICE 2 Sheets-Shet l Filed July 25. 1928 v rNvENToR LEWIS L.. GUNNINeHAM L. l.. CUNNINGHAM 1,963,957

COMPENSATED PILOT DEVICE June 26, 1934.

srwe1;sisrwet4 2 Filed July 25, 1928 60 57 60 INvE/vron Ll o i LEw/.s L .CUNNlNel-MM JJ-f, WIW

I A TToRNsye 55 be serforui in Patented June 26, 1934 rmssv l congressman mor nevica Lewis L. Cunningham, Minneapolis, Minn., as-

signor to Minneapolis-Honeywell Regulator Company, Minneapolis Delaware Y Minn., a corporation of Application July 25, 192s, serial-No. 295,221

-1 cmm. ,(ol. 15s-117.1)

This invention relates generally to improvements in devices for supplying pilot ames, and ordinarily known as pilot lights.

The essential object of the invention is to pro- 5 vide a pilot device which will, for example, control a switch in a manner to uniailingly and speedily bring the switch to one control position, and afterwards maintainA the switch in this conwhich will unfailingly and as speedily bring the A switch to another control position when the pilot flame is extinguished,l and maintain the switch in this second position regardless of changes in temperature in the urnaceror other heating apparatus with which the device is used. The proper operation of the device is therefore based on the' provision of compensating means whereby temperatures other than that provided by ythe pilot flame itself. are not eiiective to interfere with the proper operation of the device to control another device such as a switch in a predetermined manner, Another object of the invention is to provide a device inI which compensation is Imade for growth in the thermostatic elements. By the term growth is meant the permanent enlargement or increase in length occurring in metallic parts which are heated to a high temperature jfor aconsiderable period of time. It will be un- 30 derstood that a pilot light is submitted to high temperatures over long periods, and that under these l conditions the thermal elements may grow to such an extent that the accm'acy, and sometimes the proper operation of the device is entirely destroyed; A feature, therefore, of the invention is compensation for'growth of its expansible portions in a manner to maintain a delicately. sensitive operative condition notwithstanding this growth due to continued exposure of one or more thermal elementsto burner andI furnace temperatures. 9

Features of the invention include the broad ideaof 'providing a pilot device having thermally operable control elements, operative to peridrm Ytheir functions only as the'result of presence or absence of heat furnished by the llame of the pilot device itself;` of fdetails of construction o f the specific device as illustrated to show one application of the invention, and including means 50 for compensating for growth!; and for reducing liability of extinguishment oi' the pilot flame due to pressure changes in the combustion chamber, whereinv the pilot device is placed.

Advantagesand features of the invention will the descriptionof the drawings tion; and

steel,

the first tube, this second tube 20 being/supported 10e4 forming part of this application, and in sai drawings:

Figure '.1 is a vertical section through a. pilot device, constructed according to the principles oi this invention and showing the switch in openl position;

Figure 2 is a view substantiallyssimilar to Figure 1 showing the switch in closed position; trol position as long as the pilot is lighted, and

Figure 3 is a plan section on lines 3-3 of Figures i and 2; '65

Figure 4 is a vertical cross-section on lines 4-4 of Figure l. m

Figure 5 is a diagrammatic view illustrating the action of the pilot device under the varying conditions of use;

Figure 6 is a view supplementary to Figure 5;

Figure 'I is a sectional view showing a modifica- Figure 8 is an enlarged detail view illustrating the swivel connection between the innei` tube and the connecting rod.

The device has herein been shown as of the Bunsen burner type but it will be understood that the form of the device can be changed without departing from the spirit of the invention, It so will further be understood that although all details of construction Vare claimed, there is no intention to be limited to such details. I

.The base of the device is generally indicated at 1. Socketed in the base is .a burner tube 2 held g5 against withdrawal by a set screw 3. The base is drilled to provide a passage 4 with which a fuel supply pipe 5 is in threaded engagement. The passage 4 communicates with a nipple extension .7 I. entering the tube 2 todeliver the fuel upwardly 90 therein. The tube 2 has usual air intake openings 10. The tube 2, in this instance, is made in sections, and the upper end is exteriorly counterturned as at 11. A second tube 12 having a corresponding interiorly counter-turned portion is fitted over the counter-turned terminal of tube 2. The upper tube, in this instance, is' made per.- forate by a series of openings .15 spirally arranged.

It has been discovered that it isbest to construct the tube 12 from cold rolled steel, and that this 100 metal thus far gives the best result in the present embodiment of the invention; Within the tube 12 is a second tube 20, for example, of cold rolled having ahead 21 closing the upper end of by the head and centered by a counter-turned portion 22 of the head. The tubes 12 and 20, constituting 'thermal-expansion elementsv of the pilot device, may obviously be madeof any metal adaptedto withstand the temperatures to which 110 and openings 25 of the head 21.

they are subjected in use provided the lengths v and coeiiicients of expansion of the respective elements are such that they expand or contract substantially equal amounts upon equal temperature changes. The tube 20 has an exterior diameter less than the interior diameter of the tube 12 to permit ow of gas between the tubes. The inner tube 20 is open at the bottom and is unattached so that expansion can take place in a direction opposite that of tube 2, or of sections 2 and 12. The iow of gas takes place between the tubes and through openings 15 and through the inner tube These openings 25 may be considered the main ilame orifices arranged in upwardly divergent relation for the purpose of spreading the flame toward the burners 71, see Figure 5.

Although the tube 2 is herein shown as sectional, it is conceivable that a single outer tube may bev employed. The tubes 2, 12 and 20 and.

their relative arrangement may be considered as broadly constituting applicants invention, regardless of the character of the connection between the innertube, and an element to be controlled by expansible elements of the device. The tubes 12 and 20, in the specific embodiment illustrated, constitute the expansible elements of the pilot device since the other elements of the device are located considerably below the main burner as shown in Fig. 5 and are shielded to a considerable extent by an outer tube 90. The joints at the lower ends of the tubes 12 and 20 minimize conduction of heat from the thermal-expansion elements to the other parts of the device.

In explanation Yof the action of the device, it is apparent that the presence of the pilotiiame increases the temperature of the outer tube over that of the inner, and that in the presence of a burner flame this diierential in temperature is always maintained, notwithstanding the fact that the thermal elements may be additionally Velongated. It is also apparent that the now of gas toward the burning point has some effect in maintaining this temperature dierential, by shielding the inner tube 20 and conducting heat therefrom but at. present itis impossible to state what the proportional effects are. This question will be discussed below.

'Ihe ,base is formed as at 30 vertically for the passage of a connecting element, in this instance a square metal rod 31. The upper end of this rod has a swivel connection with the lower free end of the tube 20. For this purpose the lower end of the tube is cut to provide depending arms 32 each` having an opening 34, the openings being diametrically aligned to receive extensions 35 of the swivel plate 36. plate has an opening 37v slidably receiving'the rod 31. The upper end of the rod is, in this instance, attened and enlarged to providev a shoulder 38 which prevents downward movement of the rod 31. The rod 31, in this instance,`is slidable in the square opening 30 and cannot rotate. However, the swivel connection provides means whereby the tube 20 can be rotated, to properly dispose name openings 25 relative to ,the burner or burners. It will be understood that the head 21 is centered by th e counter-turned portion 22, which portion has a rotative fit in' tube 12, so that tube 20 can be rotatably adjusted. The shoulder 23 formed by this counter-turned portion preventsV downward motion of theY tube 20. y

' A feature of the invention includes the switch which is controlled by the thermostatic device, in Vthis instance for the purpose of discontinuing fuel supply to the burner, whenever the pilot light is extinguished and for maintaining the fuel supply when the pilot is lighted.

1t will be understood that thev device is now used in conjunction with heating apparatus, in which it is desirable to interrupt supply of fuel in case of failure of the pilot light, so that fuel, may not be delivered unless conditions are such that it can be lighted. Therefore, in this instance if the pilot light f the only means herein for lighting the fuel) fails the fuel supply is discontinued. For this purpose a switch is used which controls an electric circuit to a,v magnetically operable valve in a gas line which supplies the burners, see Figure 5 for a diagrammatical showing of the valve and supply pipe and electrical connections. The switch now to be described is substantially disclosed in a copendling application to Lewis L. Cunningham, Serial Number 228,855, for; Circuit controlling devices led October 26, 1927, Patent No. 1,763,094. Nevertheless this type of switch in combination with the present invention for its purposes is considered novel, particularly for the fact that this type of switch controlling device is compensated for growth in its expansible elements, due to continued exposure to furnace and/or burner temperatures. A switch operating arm is indicated at 40 and has a cylindrical drum portion 41. The drum 41 pivoted by any suitable means 42, between 105 spaced lugs 43 of the base l, the pivot 42 being in this case horizontally arranged. The lower end of the element 31 is perforated as at 39, and a band 44 is detachably connected at one end by a hook 45 passing through the opening 39. The band passes around and flatly engages the drum 41 and is connected at its opposite end by a hook 46 with the arm 47 of a spring having a coil 48 and having an opposite arm 49 terminally connected as at 50, see Figures 1 and 3., with the lugs 43. It will be understood that the spring is under tension to, maintain the band 44 in yieldable frictional engagement with the drum. 'This tensioned arrangement exerts a pulling action t0 y, secure the inner tube against outward travel. 120

Upon the arm 40 is mounted an extension 55 insulated from the arm 40, and connected thereto in any suitable manner as by rivets. Theouter end of this arm is forked as at 56, and this forked terminal engages the outer free end of a spring 125 Contact 57 suitably secured at one end to a bracket 58 in turn secured to a block of insulating material 59 mounted upon the base 1 and supported, and secured by elements generally designated 60. The spring arm. 57,',as a current carrying element, 130 cooperates withA another current carrying element designated 62, and the element 57 when released, automatically makes contact with this element 62. In Figure 5, these contacts have been respectively designated sfr-62, although in this 135 diagram the contact 57 is shown as directly se. cured to the arm 40. Referring to Figure 5, a magnetic valve is generally designatedv at 65v and includes the coil 66 land the valve operating 140 plunger 67. One side of this coil is connected by conductor 68 with contact 57 and the other side -of theV coil is connected by conductor 69 with the ligure. When the arm 4 0 moves upwardly the spring arm 57 will be released to make contact.

This closed or contact condition is shown in Fig- 156 ure 2 while the open condition is shown-in Fig` gardless of the degree of the-temperature surrounding it, and speedily responsive to always perform one intended function whenthe device is lighted, and to speedily and unfailingly perform its other intended function when the pilot flame is extinguished, the diagramsof Figures 5 and 6 have been providedin an attempt to explain the action of the devices. This explanation is partly theoretical and it will be understood there is no intention to be limited by it.

It is an lobject of the invention to, maintain a temperature difference between the` outer element 12 or its equivalent, and some form of therrnostatic element within the shell equivalent to the element 20, regardless of the temperature level or degree at the outside of the device. Referring to Figure 5 and to the first diagram designated A in this case, there is no pilot flame and, therefore, the elements are cold and the lower end of the element 20 lies, for example, at the level of the line 80. The contacts 62 and 57 are open and the valve 65 is closed. In diagram B the pilot has been lighted, .and both elements 12 and 20 haveexpanded and the contacts 62 and 57 have been closed. In this condition it is assumed that the valve 65 has been opened to permit flow of fuel to the burner or burners 71. It will be understood that under these conditions and-referring to Figure 1, gas is flowing to the flame outlets 25-15, and that gas passes between the tubes. and through the inner tube. Referring to diagram 6, beginning at line B', which corresponds to B of Figure 5,

it will be seen that both elements have expanded,.

but that the outer element represented by the line b has expanded at a greater rate than the inner element represented by line a, and that b has reached the temperature level f, while a has only reached the temperature level g. -A thermal equilibrium has been set up, in which the outer tube has attained some denite temperature above the temperatureattained by the inner tube. This relation particularly applies to the upper portionl of the device including the tubular section 12 and the tube 20; It is apparent that the outer tube is always more exposed to flame. Referring again to diagram B of Figure 5, it will be seen that While the lower end of the inner tube has risen only from line to line 81, the upper end of the device has moved a greater distance from 82 to 84. Referring to diagram C of Figure 5, it is now assumed that the burner or furnace heat has been -added to that of the pilot resulting in an additional elongation of both elements 12 and 20d. The theory is that when the furnace heat is added the outer and inner tubes are raised the same number oi degrees due to equal distribution oflieat to both, all without disturbing the differential of temperatures or the thermal equilibrium existing between the two. is represented in diagram 6 between lines B-C' in which it will be noted that the lines b-a are parallel but that there has been a temperature 4rise'from levels f-g of line B' to levels h 'i -of line C'. This maintej nanceof a temperature differential between the outer and inner tubes, is believed partly due to conduction of heatv from the flame to the outer the flame orices.

tube by the passage of unbumed gases toward I It will be noted that the lower end of the tube .20 in diagrams B and C of Figure 5 is the same, although both tubes have expanded upwardly as shown at C. It is a fact that after the device reaches the condition shown in'B of Figure 5, the lower end of the element 20 remains substantially inthe positionshown, notwithstanding that the temperature is raised exteriorly of the pilot device as a result of burner heat.

It will therefore be seen that the elements have reached what may be termed a thermal equilibrium, and that in Figure 5c, although the elements have expanded additionally, the same temperature differential has been maintained. It will be understood that although there may be a movement of the lower end of the element 20 it is always in a direction to maintain the switch, in this instance, closed.. However, there is no intention to be, limited by the statement just made, as to the immobility or substantial o immobility of the lower end of the inner element because it is shown by experiment that under these conditions the switch is never opened,

either under the condition illustrated at B orv that the burner flames are operating while the pilot name has been extinguished. It will, of course, be understood that shortly after extinguisbment of the pilotflame, the burner ameswill also be extinguished, inlthis instance due to the interruption of fuel supply, as is intended by this device. Referring to Figure 6, it will be seen-that, due to the 4extinguishinent of the pilot ame the elements b-a are cooled and reach the temperature level j, the outer cooling at a greater rate than the inner. In Figure 6, it has been additionally shown that on' extinguishment of burner flame the elements will again reach zero point as shown in line E which 'corresponds' to the condition shown at line-A. It is believed that when the pilot flame is extinguished, .there is a reduction of temperature of the outer tube, causing it to contract. If the supply of gas to the pilot has also been cut off, the inner tube expands due partly to conducted heat, and because there are no gases present to cool the inner tube. Thus in either case the thermal equilibrium is destroyed resulting in` the opening of the contacts 57-62. vThe contacts will remain in this position until the pilot It will be noted that the thickness of the inner tube is less than that of the outer. means, the heat capacity of the tube is reduced and it seems that this smaller heat capacity in conjunction with the cooling effect 'of the gases givesbetter results than if the limer tube were the same thickness as the outer. It must also be remembered that both tubes 12 and 20, if Aof the same length have substantially the .same coefficient of expansion, and in any event have substantially the same total expansion for equal By this incrementsof temperature. It will again be l noted that the discovery that making the tubes 12 and 20 of ordinary cold rolled steel will im- -invention. By the term prove results, under the present use, is also claimed. Therefore the feature of the invention is this discovery of the use of cold rolled steel in this environment.

It will be understood that the upper portion of the device herein is often arranged Ibetween- With the guard tube 90 the pressure may be equalized and therefore there is no darne extinguishment.

In reference to the compensation for growth4 it will be understood that ,the pilot is inserted in a gas furnace, for example, and that the pilot flame may be lighted for weeks. During that time the growth of the outer tube, which is the hotter of the two 'thermal elements, amounts to more than the total activity of the elements. When growth takes place the rod 31 is pulled in an outward direction and tends to rotate the arm 40 in the direction of the arrow shown in Figure 2. It will be noted that in this position of the device the contacts 57-62 are engaged. When the rod 31 is pulled outwardly, slippage between 'the element 44 and the drum 41 takes place and thus the switch elements are not injured. However, it will be seen that notwithstanding this growth and this upward or outward pull of the element 31, in case of extinguishment of the pilot fiame, the movement of the element 31 in the opposite direeticn will nevertheless obtain opening of the contacts 62,-57 as herein intended. An important feature of the invention is shown in Figure '7 in which a rod 95 is used in lieu ofthe tube. This rod has a small heat capacity, and has a low thermal conductivity. At present, the tubular sections 12 and 20 as well as the rod 95 are formed from stainless steel. This use of stainless steel for the thermal-expansionvelements is also a feature of the stainless steel is meant the class of iron alloys which are highly resistant to corrosion because of a relatively high chromium content. The rod 95 is, in the present instance, about one-tenth of an inch in diameter and is cylindrical. The rod has a low co-eicient of Aexpansion with a small thermal conductivity. The rod passes loosely through an opening 96'of the cap 9'7, which cap is boredas at 98 to providev iiame orifices, leading directly into tube 12.v Otherwise the cap 97 is generally formed and mounted in the same manner as the cap 21. The rod 95 is threaded at its lower end and these threads cooperate with threads of a socket 99 of the rod 31. pass loosely through the opening 96 it may be turned. This swivel connection is for the same general purpose as that described for the construction wherein the ,tube is used.

By having the rod 95 complish this result. Thus the whole surface of the tube 12 is substantially in contact with pilot flame. All that is necessary is to furnish that quantity of heat to the tube 12, which will maintain it at suiiiciently high temperature. At the same time the pilot fiame should be in such a position that it will ignite the main burner.

By application of heat through the openings 15 over a relatively large area of the outer surface of the outer tube 15 (or in any manner to maintain this surface at a temperature greater than any ambient temperature produced by the burner with which the device is used as a pilot) the outertube is rendered relatively insensitive to ambient or burner temperatures. The tube then acts as a shield so that the operating member 20 is shielded against transfer of heat to it suieient to expand it to open the valve or other device or to move this device to another control position.

Other influences which are believed to eiiect a cooling of the rod, tube or inner element are: radiation from that part of the inner element below the pilot fiame; radiation from the outer tube; and conduction by the inner element or its extension to the base casting, which casting is a good heat radiating body.

I claim as my invention:

A pilot device of the class described comprising, in combination, a first heat-responsive expansible tubular element arranged verticallyv and having a fixed support for the lower end thereof,

ertures around theY circumference thereofbelow the upper end, a second heat-responsive expansible element comprising a head portion swivelledon the upperend of the first heat responsive element and an elongated depending shank portion inside of said first element, a control device operatively connected to the lower end of the elongated shank portion of said second heat-responsive element, the lengths and coefiicients of expansion of saidl elements being so chosen that under thermal expansion thereof the free end of the shank portion of said second 'said element being provided with a series of apelement remains substantially stationary whenv LEWIS L. CUNNINGHAM. 

